Internal Elastomer Damper for Vehicular Propeller Shafts

ABSTRACT

Ringing noise in a tube or in tubes comprising a propeller shaft of an automotive drive is attenuated by an elastomeric ring positioned in each shaft. The elastomeric ring is a split ring, preferably made of recycled rubber, wherein the ring normally has a rectangular shape and is bent into a cylindrical shape for insertion in the tube. The outward bias of the ring is sufficient to hold the ring in place within the tube, while a gap in the material of the ring allows the ring to exert further expansive force against the inner surface of the tube while the tube is rotating. A single ring located midway between the ends of a tube is sufficient to attenuate ringing noise in one example of a tube, however a plurality of spaced rings may be used in other tube configurations to attenuate ringing noise. Preferably, the elastomeric ring has an axial extent of about 5% of the length of the tube.

FIELD OF THE INVENTION

The present invention relates to internal elastomer dampers for vehicular propeller shafts. More particularly, this invention relates to such dampers that damp noise in propeller shafts used in the drive train of automotive vehicles.

BACKGROUND OF THE INVENTION

Propeller shafts which transmit power from an engine system to the wheels of an automotive vehicle are frequently constructed with a metal tube welded to yokes that connect U-joints or other types of joints that join the engine system to the wheels. The tubes forming the drive shafts often have relatively thin walls to minimize both weight and rotating mass. These relatively thin walls tend to vibrate and generate ringing noise as it is excited by vibration from other parts of the vehicle. Currently, internal damper devices tend to be sleeves made of cardboard or foam that are relatively long. These sleeves of cardboard or foam cover almost the entire length of the propeller shaft tube and are not necessarily as effective in damping ringing noises as is desired. Thus, there is a need for a more effective, inexpensive approach to reduce ringing noises that emanate from rotating propeller shafts.

SUMMARY OF THE INVENTION

In view of the aforementioned considerations, a propeller shaft for a vehicle comprises first and second ends and at least one cylindrical tube having an inner surface and an outer surface. A ring of elastomeric material is disposed within the tube and is in contact with the inner surface of the tube at a location intermediate the ends of the tube. The ring has a minimal axial extent and radial thickness sufficient to damp ringing noise from the tube while increasing the critical speed at which the propeller shaft can rotate.

In another aspect of the propeller shaft, the elastomer material comprising the ring is rubber, and preferably is recycled rubber.

In still another aspect of the propeller shaft, the ring is axially positioned within the shaft at a location midway between the ends of the shaft.

In still a further aspect of the propeller shaft, the ring is an elastically deformed, split ring of continuous material having opposed edges forming a gap in the continuous material. The ring has an outer axially extending surface of a constant diameter. The split ring is formed of a flat polygon when in a relaxed state and retains a bias to return to the flat polygon shape when bent into a ring and inserted in the tube. The bias urges the outer axially extending surface into frictional engagement with the inner surface of the tube while the gap permits centrifugal force to further push the ring against the inner surface of the tube.

In still a further aspect of the propeller shaft, the ring has an axially extent in the range of 3% to 6% of the length of the tube and preferably has an axially extent of about 5% of the length of the tube or whatever is required to perform its damping function.

In still a further aspect of the invention, the propeller shaft is comprised of two similarly configured tubes with similar damping rings.

In still a further aspect of the invention, there is a plurality of damping rings disposed in each tube comprising the propeller shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is a top view of a drive train for an automotive vehicle;

FIG. 2 is a side view of a propeller shaft having two coupled tubes configured in accordance with the principles of the present invention;

FIG. 3 is an elevation of one of the tubes of FIG. 2;

FIG. 4 is a section taken along lines 4-4 of FIG. 2;

FIG. 5 is a rectangular blank from which a plurality of damper rings are formed; and

FIG. 6 is a single rectangular piece from which one ring is configured.

DETAILED DESCRIPTION

Referring now to FIG. 1 there is shown a drive train 10 for an automotive vehicle wherein a transmission 12 drives hubs 14 having wheels (not shown) for moving the automotive vehicle. The transmission 12 is connected to a differential 16 by a pair of tubes 18 that are coupled by universal or constant speed joints 20 to one another and to the transmission and differential. The tubes 18 together form a propeller shaft 24 for transmitting torque from the transmission 12 to the differential 16. While a pair of tubes 18 are shown, propeller shaft 24 may include only a single tube 18. In accordance with the present invention, each tube 18 includes an internal damping ring 30, which damps ringing noises that would otherwise emanate from the tubes 18.

While in FIG. 1 a drive train of an automotive vehicle is illustrated, the internal ring 30 may be used for other applications in which propeller shafts 24 are used, such as but not limited to boats or railroad engines.

FIG. 2 shows a pair of propeller shafts 18 in isolation. While a single damping ring 30 is shown in each tube 18 of FIGS. 1 and 2, the number of damping rings inserted into the tubes varies in accordance with the number needed to damp the tubes. For example, two, three or four, preferably equally spaced damping rings 30 may be inserted into a tube 18 or into each tube 18.

Referring now to FIGS. 3 and 4, each tube 18 has the coupling joints 20 at first and second ends 36 and 38 thereof, respectively, and each tube has an inner cylindrical surface 40 and outer cylindrical surface 42. Each of the damping rings or ring 30 has an axial extent 1, which is in a range of 3% to 6% of the length L of the tube 18 and preferably about 5% of the length of the tube. As is seen in FIG. 4, the damping ring 30 is made of a continuous length of elastomer material formed into a split ring having a gap 50 in the material so that the ring biases itself against the inner wall 40 of the tube 18. The bias is possible because ends 51 and 52 defining the gap 50 allow movement of the ring 30 as the ring seeks to expand and return to its former flat configuration. The gap 50 in the elastomeric material is a minimum gap. There may actually be abutment of the ends 51 and 52 forming the gap 50.

As is seen in FIG. 5, each ring 30 is formed by cutting a blank 60 of elastomeric material into the rectangular portions of FIG. 6. The rectangular portions of FIG. 6 have an outer surface 62 that in one embodiment is flat and forms into an axially extending cylindrical surface of constant diameter, which cylindrical surface 62 complements the inner cylindrical surface 40 of the cylinder 18 upon bending the ring 30 into a cylinder. There is a built in bias in the elastomeric ring 30 of FIG. 4 to return to the rectangular configuration of FIG. 6, which bias urges the outer cylindrical surface 30 into continuous abutment with the inner cylindrical surface 40 of the tube 18. A material for the elastomeric ring 30 is selected so that there is sufficient friction between the outer cylindrical surface 62 of the ring 30 and the inner cylindrical surface 40 of the tube 18 to retain the ring in a selected axial location within the tube. When the tube 18 is rotating, centrifugal force in the elastomeric ring 30 urges the ring further against the inner surface 40 of the tube to provide a further retaining force that keeps the ring from axially or circumferentially shifting in the tube.

While the outer surfaces 62 of the rings 30 in the illustrated embodiment are flat, the outer surfaces in other embodiments may have a pattern that provides functional advantages, such as increased friction or mass. Once patterns are added to the ends 50 and 52 of the blanks 60, the blanks may no longer be rectangular. The inner surfaces of the blanks 60 may also have ribs to enhance the outward bias of the rings 30.

A preferable elastomer for the ring 30 is rubber/elastomer, such as the rubber elastomer from recycled rubber, which uses rubber tire materials. Such materials provide considerable cost advantage over other materials and are highly effective in damping ringing noise from the tube 18 or from pairs of tubes 18. The elastomeric ring 30 made from recycled rubber is more effective than full-length dampers, such as the full-length dampers made of cardboard or foam.

EXAMPLE

A propeller shaft 25, such as the propeller shaft of FIG. 1, has a pair of hollow tubes 18, having the following parameters:

-   -   1.) The front (left) tube 18 has a length of 749 mm and the rear         (right) tube 18 has a length of 742 mm. Both tubes 18 have an         outside diameter of 50.8 mm and a wall thickness of 1.65 mm. The         tubes 18 are made of steel designated as SAE1026-1J and the         tubes are DOM (Draw Over Mandrel) tubes. The RPM range for noise         of the tubes 18 is from 1280 to 1680 RPM.     -   2.) The damping rings 30 are rectangles of recycled rubber bent         into circles, each with a thickness of 8 mm and a width of about         40 mm.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing form the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

1. A propeller shaft for a vehicle, comprising: a tube having first and second ends and an inner surface and an outer surface; and a dampener, said dampener being only a single-piece ring of elastomeric material which is disposed within the tube and having an outer surface in contact with the inner surface of the tube at a location intermediate the ends of the tube, the ring having an axial extent and a radial thickness sufficient to damp the tube, said ring being a flat polygon shape of the elastomeric material that is flat when in a relaxed state and when bent into ring shape for insertion into the tube retains a bias tending to return to the relaxed state and urging the outer axially extending surface into frictional engagement with the inner surface of the tube, said ring being solely of said elastomeric material with no additional support and being retained within the tube solely by frictional force.
 2. The propeller shaft of claim 1 wherein the elastomeric material is rubber.
 3. The propeller shaft of claim 2 wherein the elastomeric material is recycled rubber.
 4. The propeller shaft of claim 3 wherein the ring is axially positioned within the tube at a location midway between the ends of the tube.
 5. The propeller shaft of claim 1 wherein the flat polygon shape of the elastomeric material has opposed ends that upon bending of the flat polygon into the ring shape define a split gap in the shape of the ring enabling the ring to expand and urge the outer surface into frictional engagement with the inner surface of the tube and the gap permits permit centrifugal force to further push the outer surface of the ring against the inner surface of the tube.
 6. The propeller shaft of claim 1 wherein the ring has an axial extent in a range of about 3 to 6% of the length of the tube.
 7. The propeller shaft of claim 6 wherein the ring has an axial extent of about 5% of the length of the tube.
 8. The propeller shaft of claim 6 wherein the flat polygon shape of the elastomeric material has opposed ends that upon bending of the flat polygon into a ring shape define a split gap in the shape of the ring shape enabling the ring to expand and urge the outer surface into frictional engagement with the inner surface of the tube and permit centrifugal force to further push the outer surface of the ring against the inner surface of the tube.
 9. The propeller shaft of claim 8 wherein the elastomeric material is rubber.
 10. The propeller shaft of claim 9 wherein the elastomeric material is recycled rubber.
 11. The propeller shaft of claim 1 wherein the propeller shaft is comprised of two similarly configuring tubes with similar damping rings.
 12. A propeller shaft for a vehicle, comprising: a cylindrical tube having first and second ends and an inner surface and an outer surface; and a dampener of only a single piece of generally rectangular and flat-shaped piece of relaxed elastomeric material bent to a split-ring cylindrical shape for insertion into the tube, said ring shape having a cylindrical outer surface that is frictionally engaged with the inner surface of the tube by the bias of the elastomeric material seeking to return to it relaxed flat shape, said frictional engagement being increased by the centrifugal forces acting upon the elastomeric material during rotation of the tube so that the elastomeric material is retained against shifting within the tube solely by friction between the tube and the elastomeric material, said piece of elastomeric material having no supporting structure and being engaged with the tube solely by the friction and the centrifugal force.
 13. The propeller shaft of claim 12 wherein the piece of elastomeric material is rubber and when frictionally engaged within the tube has an axial extent of about 3 to 6% of the axial length of the tube.
 14. The propeller shaft of claim 12 in which the piece of elastomeric material is frictionally retained within the tube at approximately midway between the first and second ends of the tube.
 15. A propeller shaft for a vehicle, comprising: a tube having first and second ends and an inner surface and an outer surface; and a dampener of only a single piece of unsupported elastomeric material having opposed ends and being generally flat in a relaxed condition and being self-biased toward the relaxed condition when bent into a cylindrical ring-shape in which the opposed ends have a gap therebetween to permit expansion of the diameter of the cylindrical ring-shape, said piece of elastomeric material being located inside the tube and frictionally engaging with the inner surface of the tube so that the elastomeric material is retained solely by friction against shifting within the tube. 